Paper-based composite container for off-gassing products, and method for making same

ABSTRACT

A substantially paper-based composite container for an off-gassing product includes a paperboard can body having a substantially gas-impervious liner attached to an inner surface thereof, and a pair of substantially paper-based end closures attached to the opposite ends of the can body, each end closure defining a generally cylindrical sealing panel in contact with an inner surface of the can body. Heat-sealable materials are disposed on opposing surfaces of the sealing panel and can body. The sealing panels of the end closures are attached to the can body by heat seals. The heat seal for at least one of the end closures is discontinuous such that at least one vent channel extends through the heat seal so as to establish fluid communication between an interior of the composite container and the environment outside the composite container. The at least one vent channel is operable to vent excess gas pressure from the interior of the container.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/071,721, filed Mar. 25, 2011, which is incorporated by referenceherein in its entirety.

BACKGROUND OF THE INVENTION

The present disclosure relates generally to containers for products, andmore particularly relates to paper-based composite containers foroff-gassing products.

Paper-based composite containers for off-gassing products (e.g.,refrigerated dough) have been in the marketplace for many years. Atypical dough can has a can body formed of a paperboard body ply wrappedhelically about an axis such that a butt joint is defined between theadjacent edges of successive helical turns of the body ply. Animpervious liner is attached to the inner surface of the body ply, and apeelable label is attached to the outer surface of the body ply. Thelabel holds the butt joint closed until the consumer is ready to openthe container. The ends of the can body are closed by metal end closuresthat are seamed onto the ends of the can body. To open the container,the label is peeled off to expose the butt joint. Often, the pressure ofthe expanded dough in the container is sufficient to open the butt jointonce the label is removed. Otherwise, the butt joint is pressed orrapped against an edge of a countertop to cause it to open. The doughproduct is removed through the opening created by the separated buttjoint.

Paper-based composite containers for other off-gassing products (e.g.,roasted coffee) may also be desirable as alternatives to metal-based andplastic-based containers.

Generally, containers for off-gassing products require some type ofprovision for dealing with the pressure increase that occurs in thecontainer when the products give off gases. Various approaches to thisproblem have been tried. Some containers include vents to vent theexcess gases to the outside of the container, so that the container willnot become bulged or distorted by the internal gas pressure. Othercontainers are designed to have portions that can expand outwardly toreduce the internal pressure, but in a manner that is not aestheticallydispleasing.

Heretofore, commercial composite dough containers have employed theventing approach. In some cases, the metal end closures have been seamedonto the can body in such a way that a vent passage is defined betweenthe end closures and the can body.

BRIEF SUMMARY OF THE DISCLOSURE

The present disclosure relates to paper-based composite containers foroff-gassing products, in which the end closures are not metal but ratherare paper-based. Paper-based end closures are not readily attachable tothe can body by the seaming technique used with metal end closures, andhence a new approach to their attachment had to be developed. Theattachment technique described herein allows secure attachment of theend closures in a hermetic fashion, while also providing a ventingfunction.

In one embodiment described herein, a substantially paper-basedcomposite container for an off-gassing product comprises: a can bodycomprising a tubular wall constructed from paperboard wrapped about anaxis, the can body having opposite ends each defining an opening, thecan body further comprising a substantially gas-impervious linerattached to an inner surface of the paperboard of the can body; and apair of substantially paper-based end closures attached to the oppositeends of the can body, each end closure defining a generally cylindricalsealing panel in contact with a surface of the can body, a heat sealmaterial being disposed on a surface of the sealing panel and a heatseal material being disposed on the surface of the can body contacted bythe sealing panel.

The sealing panels of the end closures are attached to the can body byheat seals. The heat seal for at least one of the end closures isdiscontinuous such that at least one vent channel extends through theheat seal so as to establish fluid communication between an interior ofthe composite container and the environment outside the compositecontainer. The at least one vent channel is operable to vent excess gaspressure from the interior of the container.

In embodiments described herein, the heat seal having the at least onevent channel is formed by a plurality of separate, spaced heat sealregions where the heat seal materials on the sealing panel and can bodyhave been heat sealed together, thereby forming the at least one ventchannel between the spaced heat seal regions.

The spaced heat seal regions can be spaced apart in a circumferentialdirection about the can body, the at least one vent channel extendinggenerally axially of the can body.

There can be a plurality of vent channels circumferentially spacedapart.

In a specific embodiment suitable for dough containers, the paperboardof the can body is wrapped helically about the axis and a helicallyextending butt joint is defined in the can body between adjacent edgesof successive helical turns of the paperboard. The container includes alabel secured about an outer surface of the paperboard of the can body,the label comprising a polymer film. The label is scored to define ahelically extending peel strip that is located over the helicallyextending butt joint. The peel strip is removable from the can body toexpose the butt joint while leaving the remainder of the label on thecan body.

In embodiments described herein, the end closures comprise a paperboardlayer and a barrier layer. The barrier layer can comprise at least oneof polymer film and metal foil.

The present disclosure also describes a method for assembling acomposite container for an off-gassing product. In one embodiment, themethod comprises the steps of providing a can body and a pair ofsubstantially paper-based end closures of the type described above, andpositioning the end closures over the openings at the ends of the canbody and attaching the sealing panels of the end closures to the canbody by forming heat seals therebetween. The heat seal for at least oneof the end closures is formed to be discontinuous such that at least onevent channel extends through the heat seal so as to establish fluidcommunication between an interior of the composite container and theenvironment outside the composite container, the at least one ventchannel being operable to vent excess gas pressure from the interior ofthe container.

In one embodiment, the heat seal having the at least one vent channel isformed by a plurality of separate, spaced sealing elements that areheated so as to heat and soften the heat seal materials on the sealingpanel and can body at a plurality of separate, spaced regions, therebyforming the at least one vent channel between the spaced regions.

The sealing elements can be part of an expandable chuck. In this case,the heat seal can be formed by the steps of: placing the chuck in anunexpanded condition within the opening at the respective end of the canbody, the sealing panel of the end closure being located between thetubular wall of the can body and the chuck; disposing a support ringabout the end of the can body, such that the tubular wall of the canbody and the sealing panel of the end closure are disposed between thesupport ring and the chuck; and heating the sealing elements of thechuck and expanding the chuck by moving the sealing elements radiallyoutwardly to compress the sealing panel and tubular wall of the can bodybetween the sealing elements and the support ring, the heated sealingelements causing the heat seal materials on the sealing panel and canbody to be softened and to seal together at the spaced regions.

In embodiments described herein, between two and ten sealing elementsare moved radially outwardly to compress the sealing panel and tubularwall of the can body between the sealing elements and the support ring,thereby forming the heat seal to have between two and ten spacedregions. More preferably, there are between four and eight sealingelements.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Having thus described the disclosure in general terms, reference willnow be made to the accompanying drawings, which are not necessarilydrawn to scale, and wherein:

FIG. 1 is a perspective view of a heat-sealing tool, generally frombelow, for heat-sealing a substantially paper-based end closure to apaperboard can body in accordance with one embodiment of the presentinvention;

FIG. 1A is an end view of the heat-sealing tool of FIG. 1, from below,showing the sealing chuck of the tool in a retracted (unexpanded)condition;

FIG. 1B is an end view of the heating-sealing tool, from below, showingthe sealing chuck in an extended (expanded) condition;

FIG. 2 is a side view of the heat-sealing tool positioned above anassembly of a paperboard can body and substantially paper-based endclosure, in preparation for heat-sealing the end closure to the canbody;

FIG. 3 is a highly magnified detail view of a portion of FIG. 2 asindicated;

FIG. 4 is a side view of the heat-sealing tool and the can body/endclosure assembly, after the heat-sealing tool has been lowered intoengagement with the can body/end closure assembly and the sealing chuckhas been extended to expand the chuck and heat-seal the end closure tothe can body;

FIG. 5 is a highly magnified detail view to illustrate the engagement ofthe can body and end closure between the expanded sealing chuck and theouter support ring of the heat-sealing tool;

FIG. 6 is a cross-sectional view along line 6-6 in FIG. 4;

FIG. 7 is a highly magnified detail view of a portion of FIG. 6 asindicated;

FIG. 8 is a cross-sectional view through the can body and end closure ofthe completed container after the end closure has been heat-sealed tothe can body; and

FIG. 9 is a highly magnified detail view of a portion of FIG. 8 asindicated.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings in which some but not allembodiments of the inventions are shown. Indeed, these inventions may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will satisfy applicable legalrequirements. Like numbers refer to like elements throughout.

FIGS. 1, 1A, and 1B depict a heat-sealing tool 20 for use in heatingsealing a substantially paper-based end closure to a paperboard can bodyin accordance with the present invention. The tool 20 includes an outersupport ring 22 defining a central opening whose diameter isapproximately equal to (or very slightly less than) the sum of thediameter of the paperboard can body and twice the thickness of the endclosure, for reasons that will be made apparent below. The inner surface24 of the support ring defines six longitudinally extending grooves 26spaced uniformly about the circumference of the inner surface 24. Theinner surface 24 also has a conical or flared portion 24 a (FIG. 3)adjacent the lower end face 28 of the support ring 22 to help guide thecan body and end closure into the central opening of the support ringduring a heat-sealing operation, as further described below.

The heat-sealing tool 20 further includes an expandable and contractiblesealing chuck 30 that consists of six wedge-shaped segments 32 eachforming one-sixth (60°) of a 360° disk, such that the six segments 32collectively form the 360° disk. Each segment 32 has two radiallyextending side edges 34 that are linear and a radially outer edge 36that is part-cylindrical (i.e., one-sixth, or 60°, of a cylinder). Thesegments 32 are sized in outside diameter such that when the segmentshave their adjacent side edges 34 abutting each other (as in FIG. 1A),the radially outer edges 36 of the segments define a substantiallycylindrical surface having an outside diameter that is slightly smallerthan the inside diameter of a paperboard can body to be processed by theheat-sealing tool.

The tool 20 includes an arrangement for moving the segments 32 radiallyoutwardly in unison so as to increase the outside diameter of thesubstantially cylindrical surface that the segments collectively form.In the illustrated tool 20, this arrangement comprises a longitudinallymovable ram 40 connected at its lower end to a cam arrangement (notvisible in the drawings) that engages cam surfaces on the segments 32.The ram 40 passes down the center of a hollow guide tube 42 affixed atits lower end to the support ring 22. Moving the ram 40 downwardrelative to the segments 32 causes the cam arrangement to urge thesegments 32 radially outwardly. The tool 20 also includes an upper plate44 rigidly connected by connecting members 46 to the support ring 22,and has means (not shown) for urging the upper plate 44, and thereforethe support ring 22, downward independently of the movement of the ram40, for reasons that will be made apparent below.

Turning to FIGS. 2 through 5, a heat-sealing operation employing thetool 20 is now described. FIGS. 2 and 3 depict the tool 20 positionedatop an assembly consisting of a paperboard can body 50 and asubstantially paper-based end closure 60. The can body 50 has acylindrical or tubular form and is open at both ends. The can body 50 isformed substantially of paperboard and includes a heat-sealable materialon its inner surface. The heat-sealable material can be part of agas-impervious liner 52 attached to an inner surface of a tubular wall54 (FIG. 7) constructed from paperboard wrapped helically or convolutelyabout an axis of the tube. The end closure 60 can comprise a laminate ofmultiple layers, including a heat-sealable layer 62 and a paper layer 64(FIG. 7). The end closure 60 is formed (preferably prior to placing itatop the can body 50) so that it has a disk-shaped central portion 66, acylindrical sealing panel 67 that extends upwardly from the centralportion and is sized to fit closely into the top end of the can body 50,and an outer peripheral portion 68 that extends radially outwardly fromthe top end of the sealing panel 67 for a distance sufficient to provideenough material to be wiped down the outer surface of the top end of thecan body 50.

As shown in FIG. 3, the heat-sealing tool 20 initially is in a startingposition in which the sealing chuck 30 is in its retracted (contracted)state and has its lower surface closely adjacent or abutting the topsurface of the central portion 66 of the end closure. The tool 20 as awhole can be lowered, or the can body 50 and end closure 60 assembly canbe raised relative to the tool 20, to cause the contracted sealing chuck30 to push the central portion 66 of the end closure down into the topend of the can body 50 until the outer peripheral portion 68 is abuttingor nearly abutting the top edge of the can body 50. In this condition,the support ring 22 of the tool 20 is in a raised position slightlyspaced above the top edge of the can body 50 and the outer peripheralportion 68 of the end closure 60 as shown in FIG. 3.

FIGS. 4 and 5 illustrate the next step of the heat-sealing operation.The support ring 22 is moved downward so that the upper end of the canbody 50 is received inside the central opening of the support ring, inthe radial space between the inner surface 24 of the support ring andthe outer surface of the sealing chuck 30. Substantially concurrently,the ram 40 is moved downward to cause the sealing chuck 30 to beexpanded in diameter so that the end closure's sealing panel 67, the canbody 50, and the outer peripheral portion 68 of the end closure areradially compressed between the expanded chuck 30 and the support ring22. The sealing chuck 30 and the support ring 22 are heated sufficientlyto cause softening or melting of the heat-sealable materials on the canbody 50 and end closure 60. Specifically, with reference to FIG. 7, theheat-sealable layer 52 on the can body and the heat-sealable layer 62 onthe end closure 60 are softened or melted and fuse together (note:layers 52 and 62 are shown with spacing between them in FIG. 7, forclarity of illustration; in reality they are in contact with eachother). The heating is then discontinued and the support ring 22 and ram40 are retracted and the finished can/end closure assembly is removedfrom the tool 20 to complete the heat-sealing operation. An end closurecan be attached to the opposite end of the can body in the same fashionas just described.

The tool 20 produces unique features in the completed can/end closureassembly, which are now described with reference to FIGS. 6 through 9.In particular, because there are circumferential gaps between adjacentsegments 32 of the expanded sealing chuck (as best seen in FIG. 1B), theheated segments 32 produce spaced heat seal regions where the heat sealmaterials on the sealing panel 67 and can body 50 have been heat sealedtogether. The spaces between those heat seal regions are areas where thesealing panel 67 of the end closure is not heat-sealed to the can body50, since the heat-sealable layers 52, 62 of these components are notheated and fused together in these areas. The result, as seen in FIGS. 7and 9, is a series of channels 70 between the sealing panel 67 and thecan body 50. These channels 70 act as vents that can allow excess gaspressure inside the container to be vented to the outside of thecontainer. It should be noted that FIGS. 7 and 9 depict the channels 70as being open radial spaces, but this is mainly for clarity ofillustration. In reality, the sealing panel 67 and can body 50 maycontact each other in the region of the channels 70, but are not sealedor otherwise attached together in the channels 70, which is what allowsexcess gas pressure to escape through the channels.

This venting action is also aided by similar channels 72 defined betweenthe outer peripheral portion 68 of the end closure and the outer surfaceof the can body 50. The channels 72 are formed as a result of thegrooves 26 in the inner surface of the support ring 22, which arealigned with the gaps between sealing chuck segments 32 and allow theouter peripheral portion 68 of the end closure in the regions of thegrooves to “flow” outwardly into the grooves. The channels 70 on theinner side of the can body can communicate with the channels 72 on theouter side because the end closure is not sealed to the very top edge ofthe can body, as best seen in FIG. 5.

A container assembled in accordance with the foregoing description canbe used for containing a product that off-gases or causes increasingpressure within the container, such as refrigerated dough or roastedcoffee. Excess pressure in the container is vented through the channels.The threshold pressure at which venting will occur can be controlled bysuitably designing the number and sizes of the gaps between sealingchuck segments 32 and correspondingly the number and sizes of thegrooves 26 in the support ring 22, thereby controlling the number anddimensions of the channels 70, 72.

As one non-limiting example, the sealing panel 67 can have a thicknessof about 0.015″ to about 0.020″, and a circumference of about 9.5″. Thecollective circumferential width of the channels 70 (i.e., the sum ofthe circumferential widths of all channels) can be about 0.095″ to about1.5″, or on a percentage basis, about 1% to about 16% of thecircumference of the sealing panel. The collective circumferential widthmore preferably ranges from about 2% to about 10%, and still morepreferably about 4% to about 6% of the circumference. As one example,there can be six channels 70 each 0.060″ in circumferential width, for acollective circumferential width of 0.36″, or 3.8% of the circumference.It will be understood that the circumferential widths of the channels 70correspond to the circumferential widths of the gaps between sealingsegments 32 at the radially outer surface 36 of the sealing chuck 30,and the circumference of the sealing panel 67 is substantially equal tothe circumference of the outer surface 36 of the sealing chuck 30. Thus,another way of specifying the preferred channel/gap widths is to requirethat the collective circumferential width of the gaps between segments32 at the radially outer surface 36 of the sealing chuck 30 ranges fromabout 1% to about 16% (more preferably about 2% to about 10%, and stillmore preferably about 4% to about 6%) of the circumference of the outersurface 36.

Many modifications and other embodiments of the inventions set forthherein will come to mind to one skilled in the art to which theseinventions pertain having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it is tobe understood that the inventions are not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

What is claimed is:
 1. A method for assembling a composite container foran off-gassing product, comprising the steps of: providing a can bodycomprising a tubular wall constructed from paperboard wrapped about anaxis, the can body having opposite ends each defining an opening, thecan body further comprising a substantially gas-impervious linerattached to an inner surface of the paperboard of the can body;providing a pair of substantially paper-based end closures, each endclosure defining a generally cylindrical sealing panel, a heat sealmaterial being disposed on a surface of the sealing panel, and a heatseal material being disposed on a corresponding surface of the can body;and positioning the end closures over the openings at the ends of thecan body and attaching the sealing panels of the end closures to the canbody by forming heat seals therebetween; wherein the heat seal for atleast one of the end closures is formed to be discontinuous such that atleast one vent channel extends through the heat seal so as to establishfluid communication between an interior of the composite container andthe environment outside the composite container, the at least one ventchannel being operable to vent excess gas pressure from the interior ofthe container.
 2. The method of claim 1, wherein the heat seal havingthe at least one vent channel is formed by a plurality of separate,spaced sealing elements that are heated so as to heat and soften theheat seal materials on the sealing panel and can body at a plurality ofseparate, spaced regions, thereby forming the at least one vent channelbetween the spaced regions.
 3. The method of claim 2, wherein thesealing elements are part of an expandable chuck, the heat seal beingformed by the steps of: placing the chuck in an unexpanded conditionwithin the opening at the respective end of the can body, the sealingpanel of the end closure being located between the tubular wall of thecan body and the chuck; disposing a support ring about the end of thecan body, such that the tubular wall of the can body and the sealingpanel of the end closure are disposed between the support ring and thechuck; and heating the sealing elements of the chuck and expanding thechuck by moving the sealing elements radially outwardly to compress thesealing panel and tubular wall of the can body between the support ringand a radially outer surface of the chuck formed by the sealingelements, wherein expansion of the chuck causes circumferential gaps todevelop between adjacent sealing elements at the radially outer surface,the heated sealing elements causing the heat seal materials on thesealing panel and can body to be softened and to seal together at thespaced regions.
 4. The method of claim 3, wherein between two and tensealing elements are moved radially outwardly to compress the sealingpanel and tubular wall of the can body between the sealing elements andthe support ring, thereby forming the heat seal to have between two andten spaced regions.
 5. The method of claim 3, wherein between four andeight sealing elements are moved radially outwardly to compress thesealing panel and tubular wall of the can body between the sealingelements and the support ring, thereby forming the heat seal to havebetween four and eight spaced regions.
 6. The method of claim 3, whereinwhen the chuck is expanded to compress the sealing panel and tubularwall of the can body between the sealing elements and the support ring,a collective circumferential width of the gaps between the sealingelements at the radially outer surface of the chuck ranges from about 1%to about 16% of a circumference of the radially outer surface of thechuck.
 7. The method of claim 6, wherein when the chuck is expanded thecollective circumferential width of the gaps between the sealingelements at the radially outer surface of the chuck ranges from about 2%to about 10% of the circumference of the radially outer surface of thechuck.